This is a Phase I/II, blinded, randomized, multi-center, 48-week study of two doses of ABT-378/Ritonavir in combination with two nucleoside reverse transcriptase inhibitors (at least one of which the patient has not previous received) and Nevirapine in protease inhibitor experienced, otherwise healthy, HIV-infected patients. The primary objective of the study is to assess the safety, tolerabillity, and antiviral activity of ABT-378/Ritonavir in combination with two nucleoside reverse transcriptase inhibitors (at least one of which the patient has not received before) and nevirapine in protease inhibitor experienced HIV-infected patients. The secondary objective is to determine the steady-state pharmacokinetic profile of ABTR-378/Ritonavir and Nevirapine in protease inhibitor experienced HIV-infected patients.